Flexible contour turbine nozzle for tight closure

ABSTRACT

In a two shaft, axial flow, reversing gas turbine, hot turbine gases from the blades of the compressor turbine are selectively directed through a variable nozzle ring to rotate the turbine wheel of the load shaft in either one or the other direction. The variable nozzle ring comprises two concentric rings of adjustable vanes, one of which may be open while the other is closed. The present invention is directed toward controlling leakage losses through the vanes when closed and also toward limiting turbulence and hence aerodynamic losses in the vanes when open.

United States Patent [191 Hendrickson et al.

FLEXIBLE CONTOUR TURBINE NOZZLE FOR TIGHT CLOSURE Inventors: Robert L. Hendrickson, Scotia;

George W. Scheper, Jr., Schenectady, both of NY.

Assignee: General Electric Company,

Schenectady, NY.

Filed: May 1,1972

Appl. No.: 249,614

US. Cl 415/152, 60/39.17, 415/153 Int. Cl. F0ld l/30, F020 1/06 Field of Search... 415/152, 153, 154, 160, 161,

References Cited UNITED STATES PATENTS 11/1966 Scheper,Jr.... 10/1928 Moody FOREIGN PATENTS OR APPLICATIONS France 415/163 [451 Feb. 5, 1974 188,286 2/1956 Austria 415/161 Primary Examiner-l-lenry F. Raduazo Attorney, Agent, or Firm-John F. Ahem; James W.

Mitchell [57] ABSTRACT In a two shaft, axial flow, reversing gas turbine, hot turbine gases from the blades of the compressor turbine are selectively directed through a variable nozzle ring to rotate the turbine wheel of the load shaft in either one or the other direction. The variable nozzle 9 Claims, 7 Drawing Figures PATENTEU 5 74 SHEET 2 OF 3 F|G.2 (PRIOR ART) F I63 (PRIOR ART) BACKSIDE LEAKAGE -"VANE BACKSIDE PATENTED 5 74 SHEET 3 OF 3 ADJACENT vANE TAIL ADJACENT vANE TAIL ADJACENT vANE TAIL FLEXIBLE CONTOUR TURBINE NOZZLE FOR TIGHT CLOSURE BACKGROUND OF THE INVENTION This invention was made under contract with the United States Government under Contract O-355l with the United States Maritime Administration of the Department of Commerce. The U.S. Government is licensed in accordance with the terms of the aforesaid contract and has reserved the rights set forth in Sections 1 (f) and 1 (g) of the Oct. 10, 1963 Presidential Statement of Government Patent Policy.

In a two shaft, axial flow reversing gas turbine of the type disclosed in the U.S. Pat. Nos. 3,286,982 and 3,286,983, both of which have issued on Nov. 22, e

1966, to G. W. Scheper, Jr. and have been assigned to the assignee of the present invention; the motive fluid (hot gas from a compressor turbine) is selectively directed through one or the other of concentric nozzle rings in order to turn a turbine wheel, in a clockwise or counterclockwise direction, the wheel being attached to the load rotor shaft of a gas turbine. This type of gas turbine is particularly useful for marine propulsion where it is necessary to move a ship ahead or astern by changing the direction of shaft rotation. In order to accomplish the change in direction of the load shaft, the vanes of the concentric nozzle .rings are selectively opened or closed as set forth in the above cited patents.

As is disclosed in the latter U.S. Pat. No. 3,286,983, one problem, which has occurred, is leakage of motive fluid through the closed portion of the nozzle ring at the nozzle vane tip. This is not such a serious problem when the ship is traveling astern since that situation occurs infrequently and is usually not conducted under full power. The critical situation occurs when the ship is traveling ahead and it is desirable to provide as complete a closure of astern nozzle vanes as possible. One solution to the problem has been set forth in the cited U.S. Pat. No. 3,286,983 in that the nozzle vanes were notched in their backsides to effect a more complete closure of that portion of the nozzle ring. While this solution represents a partial answer to the leakage problem, it creates a problem when the nozzle vanes are open, to wit: motive fluid turbulence and hence aerodynamic losses are experienced over the backside portions of the nozzle vanes due to the notches. Thus changing the contour of the backsides of the nozzle vanes to effect a more complete closure will give rise to aerodynamic inadequacies under certain operating conditions.

It is therefore one object of the present invention to provide an improved reversible axial flow gas turbine.

Another object of the invention is to provide an improved gas turbine adjustable nozzle ring structure for accomplishing shaft reversal in an axial flow gas turbine.

Still another object of the present invention is to provide adjustable nozzle vanes which will effect a tight closure when the nozzle ring is closed and prevent aerodynamic losses when the nozzle ring is open.

Other objects and advantages will become apparent from the following description of various emobidments of the invention, and the novel features will be particularly pointed out hereinafter in the claims.

SUMMARY OF THE INVENTION In a two shaft, axial flow, reversing gas turbine, load storing the smooth aerodynamic contour of the vanes when they are opened. Such means may include a resilient notch cover mounted adjacent the notch which may be depressed into the notch upon vane closure. Other means include a pressure activated notch cover or a spring loaded notch cover.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial side elevation view of an axial flow, two shaft, reversing gas turbine including a compressor driving turbine wheel, a variable nozzle ring, a turbine wheel fixed to a load shaft and an exhaust section.

FIGS. 2 and 3 show plan views of nozzle vanes according to the prior art as exemplified by the U.S. Pat

' No. to Scheper .lr., 3,286,983 supra.

FIG. 4 is a cross section taken at IVIV in FIG. 1 showing the preferred embodiment of the present invention.

FIGS. 5, 6 and 7 are similar to FIG. 4 showing alternative embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 of the drawings, an axial flow, two shaft, reversing gas turbine 11 includes a flow path 13 defined by the gas turbine casing 14, duct walls 15 and a flow divider l7. Duct walls 15 and divider l7 conduct hot motive gases from a compressor driving turbine wheel 21 on one shaft, to a turbine wheel 23 which turns the load shaft 25. The turbine wheel 23 is comprised of two concentric annular rings of turbine buckets or blades. The radially outer blades 23a are curved in order to impart forward drive to the rotor shaft while the radially inner blades 23b are curved in a reverse direction to impart reverse rotation to the rotor shaft for astern drive. The two annular rings of rotor blades are separated by a platform ring 23c. Gases passing through thp compound turbine wheel then exit into an exhaust path section 27.

An adjustable flow path deflector 35, according to U.S. Pat. Application Ser. No. 208,840 filed Dec. 16, 1971 for l-Ieinhold and l-Iuber and assigned to the assignee of the present invention, is located immediately adjacent to the exhaust end of the radially inward blades 23b of the turbine wheel. The function and construction of this part, if not apparent from FIG. 1, is explained in the cited U.S. Pat. Application as well as other details of the reversing gas turbine construction.

The adjustable nozzle ring 41, includes two concentric nozzle rings comprising radially outer vanes 41a and radially inner vanes 41b. These vanes may each be controlled by levers 43 and 44 which operate hollow shafts 45 and 46 respectively rotating vanes 41a and 41b respectively. Separating the two concentric nozzle rings is a sealing lip platform 51 which cooperates with adjacent turbine parts. The nozzle rings selectively direct motive fluid to either the radially inner or radially outer blades of the compound turbine wheel.

In FIG. 2 there is shown a pair of nozzle vanes which may be circumferentially arrayed about a nozzle ring with the vane tips extending radially outward in a divergent fan like construction when the nozzle ring is in an open position. It should thus be noted that the exit angle at the tips is typically greater than the exit angle at the roots because of the above mentioned divergent construction. Upon closing the nozzle ring, as shown, adjacent vanes will contact somewhere between the root and the tip, interfering with complete closure and leaving a substantial open portion between the vane tips resulting in leakage losses.

FIG. 3 shows the remedy applied in US. Pat. No. 3,286,983 wherein notches were formed on the backside or downstream side of the nozzle vanes to accommodate adjacent vane tails from root to tip thereby providing a tight closure. This improved the closure problems but introduced aerodynamic losses due to turbulence created at the notches. According to U.S. Pat. No. 3,286,983 this was acceptable because the aerodynamic losses would occur only during astern operation if only the radially inward vanes were notched and meanwhile complete closure of the astern vaneswas obtained during ahead operation. The astern vanes having been compromised to provide tight closure. The present invention improves performance in both the astern and ahead mode of operation, reducing leakage losses and eliminating turbulence due to the notches. The present invention may be applied to both the radially inner and radially outer nozzle ring vanes or may be applied only to the radially inner vanes if leakage through the radially outer vanes during astern operation was found to be acceptable without vane modification.

Referring now to FIG. 4, two adjacent nozzle vanes 41 are shown. No designation of a" or b is applied since the invention may be applied to both the radially inner and radially outer nozzle vanes. One nozzle vane is shown contacted by an adjacent nozzle tip. According to the presentinvention the downstream side of the nozzle vane is formed with a notch 61 a lip 62 at one end of the notch and a recess 63 formed within the notch. A notch cover 64 is pivoted about an integral hinge 65 in the vane' and a dished washer spring 66 abutting the the notch cover is disposed within the recess. The operation of the above construction will be hereinafter described.

Referring now to FIG. 5, another embodiment of the present invention will be described. Again the vane 41 may have a notch 71, a lip 72 and a recess 73 formed within the notch. A notch cover 74 is pivoted about an integral hinge 75 in the vane and a helical spring 76 abutting the notch cover is disposed within the recess.

FIG. 6 shows a portion of the backside of a nozzle vane and an adjacent vane tip prior to the adjacent vane tip depressing a resilient notch cover 84 into a notch 81. The resilient notch cover may be welded at one end to the backside of the nozzle vane.

FIG. 7 shows still another embodiment of the present invention wherein a notch 91 is formed in the backside of a nozzle vane. A resilient notch cover 94 may be welded at one end to the vane backside and may be formed with a piston 95 at its free end. The piston is partially disposed in a chamber 96 and activated by The operation of the present invention is apparent from the drawings. Referring especially to FIG. 4, when the nozzle vanes are in a closed position the adjacent nozzle tails will depress the notch cover into the notch thereby providing a tight closure. Thereafter when the nozzle is opened, the notch cover will be pushed by the spring until it engages the lip whereupon it will conform to the original contour of the nozzle vane providing a smooth aerodynamic surface.

While there is shown what are considered to be the preferred embodiments of the invention, it is of course understood that various other modifications may be made therein and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A reversible axial flow turbine comprising:

a source of hot motive fluid;

a turbine rotor having inner and outer coaxial, concentric blade rings thereon, one ring comprising blades of reverse curvature for effecting rotation opposite that of the other ring;

a variable area nozzle ring for each of said turbine rotor blade rings comprising inner and outer concentric nozzle rings of radially extending adjustable vanes having aerodynamic contour;

at least one ring of said adjustable vanes having a notch formed on the backside of each vane disposed to receive an adjacent vane tail therein when the nozzle ring is closed for reducing leakage of hot motive fluid through the vane ring; and,

a notch cover on the backside of said vane disposed to overlie said notch and biased outwardly therefrom whereby when the nozzle ring is open the aerodynamic contour of the nozzle vane backside is restored.

2. The turbine recited in claim 1 wherein the notch cover is a leaf spring fixed at one end to the vane and cantilevered to overlie said notch.

3. The turbine recited in claim 1 wherein the notch cover is pivotally mounted on said vane and biased outwardly by a spring.

4. The turbine recited in claim 1 wherein the vane includes a pressurized chamber having an opening therein and the notch cover is formed with a piston partially disposed in said pressurized chamber through said opening whereby pressurizing said chamber causes the outward biasing of said notch cover.

5. The turbine recited in claim 1 wherein the notch cover is depressed into said notch when the nozzle ring is closed.

6. The turbine as recited in claim 3 wherein the spring is contained in a recess in said notch.

7. The turbine as recited in claim 6 wherein the spring is a dished washer spring.

8. The turbine as recited in claim 6 wherein the spring is a helical spring.

9. The turbine as recited in claim 3 wherein the notch is formed with an overhanging lip limiting the outward bias of said notch cover.

I. 4 4 i t 

1. A reversible axial flow turbine comprising: a source of hot motive fluid; a turbine rotor having inner and outer coaxial, concentric blade rings thereon, one ring comprising blades of reverse curvature for effecting rotation opposite that of the other ring; a variable area nozzle ring for each of said turbine rotor blade rings comprising inner and outer concentric nozzle rings of radially extending adjustable vanes having aerodynamic contour; at least one ring of said adjustable vanes having a notch formed on the backside of each vane disposed to receive an adjacent vane tail therein when the nozzle ring is closed for reducing leakage of hot motive fluid through the vane ring; and, a notch cover on the backside of said vane disposed to overlie said notch and biased outwardly therefrom whereby when the nozzle ring is open the aerodynamic contour of the nozzle vane backside is restored.
 2. The turbine recited in claim 1 wherein the notch cover is a leaf spring fixed at one end to the vane and cantilevered to overlie said notch.
 3. The turbine recited in claim 1 wherein the notch cover is pivotally mounted on said vane and biased outwardly by a spring.
 4. The turbine recited in claim 1 wherein the vane includes a pressurized chamber having an opening therein and the notch cover is formed with a piston partially disposed in said pressurized chamber through said opening whereby pressurizing said chamber causes the outward biasing of said notch cover.
 5. The turbine recited in claim 1 wherein the notch cover is depressed into said notch when the nozzle ring is closed.
 6. The turbine as recited in claim 3 wherein the spring is contained in a recess in said notch.
 7. The turbine as recited in claim 6 wherein the spring is a dished washer spring.
 8. The turbine as recited in claim 6 wherein the spring is a helical spring.
 9. The turbine as recited in claim 3 wherein the notch is formed with an overhanging lip limiting the outward bias of said notch cover. 